Compiz
The compositing window manager that in 2006 made the Linux desktop wobble, spin and catch fire — on an ordinary graphics card.
David Reveman at Novell released Compiz in January 2006, originally on top of Xgl, an X server that pushed everything through OpenGL. Red Hat answered with AIGLX, which delivered the same capabilities inside the regular server, and that is the approach that stuck. The same year the project forked into Beryl; in 2007 the two reunited as Compiz Fusion.
The effects — rubbery windows, the desktop cube, windows that burned away on close — were demoed at every trade show and switched off at home within a week. What remained was more useful: translucency, smooth transitions and an end to flicker. Ubuntu's Unity ran on Compiz until 2017, when Ubuntu moved to GNOME.